If you have tight hips, this move is for you. I recommend starting off slow to master the movement; think about creating the largest circle you can with your knee while maintaining proper form. You can and should reverse the direction of this exercise to hit the hip joint from every angle.
Start on all fours with your hands directly under your shoulders and your knees directly under your hips.
Moving from your hip, lift your left knee up off of the ground. From here draw and imaginary semi-circle with your left knee, slightly opening your hip, moving your knee forward.
Complete the motion by bringing your left knee back underneath your left hip. Avoid shifting your weight to the right side. This counts as one rep.